Many mobile devices include accelerometers. For example, due to the recent advancement in micro-electrical mechanical systems (MEMS) technologies, MEMS based accelerometers may be integrated into many hand held devices, such as cellular phones and cameras, to improve user interaction. Three-axis accelerometers may also be used to infer a user's physical activity, which may be used for a variety of applications, such as fitness and health monitoring applications, or context-aware applications.
In order to be useful for many applications such as but not limited to activity inference, the initial orientation of the accelerometer must be known. Typically, the orientation may be fixed or determined in advance. Some accelerometers may need to be worn in a precise known location, such as centered on the right side of the waist.
It is with respect to these and other considerations that the following improvements are made.